Method of producing cast-iron of high qualities of strength in alpha cupola furnace



Nov. 8, 1932. K 'EMMEL l METHOD op PRoDUcING cAsT IRON op HIGH QUALITIESoF STRENGTH 1N A cupo-LA FURNACE Filed March 6, 1928 Patented Nov. 8,1932 UNITED STATES PATENT ori-wlan KARL Emmi., or MULHmM-BUHB, amm

IETHOD F PRODUCING CAST- IRON 0F HIGH QUALITIES 0F STRENGTH IN' A.CUPOLA. FURNACE Application led March 6, 13928, Serial No.

Thorough experiments have proved that a smelting made according to the'process for the production of iron castings with a low carbon contentand of particularly high qualities, as described in the specication ofmy prior Patent No. 1,683,714, has the property of maintaining said hi hqualities of strength even if it is subjecte to a subsequentcarbonization.

The invention is based upon this fact, and its object is, as afurtherimprovement or modification of the process afore-mentioned, toproduce iron castings which beside their high qualities of strength havea particular favorable capability of being conveniently worked.

The improved method forming the subject matter of the present inventionconsists in, first, producing, according to the process aforementioned,a superheated smelting of a total carbon content of about 2-3% fromacharge whereof thev iron portion consists of at least 50% of iron lowin carbon while the remainder of the iron contents consists of iron richin carbon and of suitable admixtures and wherein the quantity of cokeemployed amounts to between 9 and 13% of the total charge that issubmitted to a varying blast pressure of between 400 and 80() mms. watergauge pressure,l and, subsequently, carbonizing said smelting low incarbon to a higher carbon content, for instance 3.4-3.6%.

Beside the favorable capability of working the product obtained, whichdoes not in any way impair the high qualities of strength of the same,the further advantage is attained that the subsequent carbonizationreduces the solidification point of the smelting and fav orablyinfluence the casting capability of the latter.

The improvedv method can, invention, for instance, within'the samecupola furnace, in which the' melting of the charge was done, by thesubsequent carbonization of the superheated smelting low in carbon beingproduced in the lower art ofthe cupola furnace by the heat-l ing co e ofthe latter. The degree of carbonization can be controlled by a'regulation of the carbonization time or of the height of the bath in thereceiver of the cupola furaccording to the also be carried out 259,609,and in Germany march 15, 1927.

nace, or by a change of the height of the meltod may be satisfactorilypracticed, isI illus-.

trated by way of example. The shell or wall of the furnace is indicatedat 10, upper and lower tuyres at 11 and 12 respectively, and tappingholes at 13 and 14. The body of coke is shown to occupy the lower end ofthe smelting chamber, below the tuyres, and the charge of iron andcarbon the bulk of the remainder of the space available. Therelationships of the diameter of the combustion space to the distancesof the tuyres 4from the bottom, respectively, are set forth, the lowerset of tuyres being preferably located at a distance above the bot-tomequal to three fourths of the diameter of the combustion space, and theupper tuyres being one and one fourth diameters above the bottom. Thesedimensions are, of course, approximate.

I am aware that it has already been proposed for instance in the U. S.Patent 1,336,256 (Muntz and Roubien) to work a cupola furnace with adeep lower part in such a way that, first, the heating coke isbrought-to incandescence by an upwardly directed blast and, then, thecasting scraps are molten, which smelting is to form at the rear of thetap-hole at the bottom of the furnace a liquid cast-lron layer of slowsolidification due to its less high carbon content. Only then, theremaining charge or burden consisting mainly of steel scraps is to meltdown.\ The result of said proposal would be-like in the last-mentionedmode of carrying out the improved method forming the subject matter ofthe present invention-Aa carbonization of theVv steel smelting inthelower part of the furnace, which result has, however, been neitherforeseen nor stated as a consequence of said proposal, for otherwise'vthe precaution against solidification at the rear of the tap-ho e is notunderstood. Furthermore, said proposal of` the Patent 1,336,256 did notaim at the superheating of the smelting or at the production of asmelting of articularly favorable casting capability. his is alsocontradicted by the fear in said proposal of a solidification ofthesmelting already in the furnace itself. Said known proposal had for itsonly object to cheapen the charge principally desi ed for an adjoiningBessemer process, wit out the perception of the high value, of the ideaupon which the present invention is based, for the\ production of ironcastings of high qualities of strength, and so on.

The present invention has for its Object, to produce in a simple cupolafurnace such castings of specially high values, which possess besideshigh resistance values still specially favorable capability fortreatment. It conslsts in utilizing the high superheating -which in thecupola furnace 1s due to the stee containing smelting, to obtain a gooddistribution of the carbon at subsequent carbonization without thenecessit7 to use, as hitherto, several devices for sme ting andcarbonizing, only one single device and only one single smeltingoperation being re uired. Thisis obtained by arranging the evicespecially for the lsubsequent carbonizing by suitably spacing the tuyresfrom the bottom plate of the furnace and by roviding a suitable numberof rows of tuyeres and further by conducting the operation of thefurnace in such a manner, that a very high temperature of the smeltingis attained.

At an inner diameter of the furnace of 900 mm there has been obtained,for instance at a distance of 450 mm. of the tuyres from the bottomplate of the furnace, 2,8 to 3,1% of carbon content o f the cast iron.If however the first row of tuyres is spaced 600 mm from the furnacebottom, the cast iron shows a percentage of carbon from 3 to 3,4%. rThis shows that a subsequent carbonizing of the superheated smelting,obtained by the smelting, process with high steel charge, is the morepossible the eater the distance of the nozzles from the ace bottom isselected.

The layer of the hottest workin ofthe furnace is situated about 30 cms.a ove the tuyres and, if -there are several rows of 'tuyres, higher plusthe -distance between the several Vrows of tuyres. Y There have been.

proposed therefore two means for the subsequent carbonizing, i. e. firsttheincreasing of the distance between the furnace bottom and the firstrow of tufyres and secondly increasing the heigiltl;l o the layer of thehottest furnace wor g above the tuyres b arranging severa rows oftuyres. e producing develops in such a manner that first in thespecially thick layer of the ,hottest furnace working above the tuyresthe steel charge is heated to the highest 'ble temperature, and thisexcessively heatedv smelting is then su uently thoroughlyY carbonizedunderneath t e tuyres 1n the comparatively high layer of IilJin coke.This ce in the furnace between the irnace ubottomandthetu'yresisilledwithcokeina manner known per se. The molteniron takes up the carbon from this coke.

According1 to the smelting process of the invention, t e object ofplacing the layer of the hottest furnace working at a higher lever is,to obtain the highestpossible superheating in' order to subsequentlycarbonize thorou hly this highly heated smelting with the ai of a highlayer of filling coke. From the high super eatlng of the smeltingresults a quite specially fine distribution of the carbon in thesmelting so that a product can be obtained, which is equal to the bestcast ironproducts known at present,

The improved method can, for instance, be put into practice in such away that the smeltin of lowcarbon content attained above the tuyeres andheated to steel melting temperature is passed through and carbomzed inthe coke-filled smelting receiver prior to its admission to theforehearth. Also in this case the degree of carbonization of thesmelting can be controlled by a regulation of the bath in the smeltingreceiver. With a long stay of the smelting in the lower part of thefurnace serving as a carbonization chamber, or with a slow passage ofthe smeltin therethrough, 'the latter will receive a hig er carboncontent a larger velocity.

The height of the carbonizing smeltingreceiver, or the height of thebath respectively, can be regulated with a maintenance ofthe height ofthe tuyres, by illin -in the bottom end of the lower part of the rnacewith suitable substances, such as sand, firebricks, or the like formaking the bottom of the furnace of di erent heights.

The subsequent carbonization of the smelting low in carbon and thustaking indeed advantage of the maximum temperatures in the furnace, canalso take place substantially or in addition to the afor-mentionedprovisions by performing the melting process of the charged low-carboniron, for a comparatively high layer of hi hest temperature, above aswell as within t e uppermost artial layer thereof, and that in such aWay or the smeltthan with a shorter stay and withl ing produced hasoccasion to be heated to, or Y at least approximately to ature in thefurnace. Additionally thereto, the superheated smelting low in carbonthus formed has then in the lower partial'layers said highesttemperhand, by a systematic utilization of the ef.- 13o eated metalthrough a body o fects of such a zone of hottest furnace working a,controllable subsequent carbonization of a superheated smeltinglow incarbon can be obtained, and how, on the other hand, the final carboncontent of the product leaving the furnace can be directly influenced bya regulation of height of said layer or zone of hottest furnace working.

It may be noted that a regulation of the height of such a layer or zoneof hottest furnace working can also be attained with the aid of onesingle row of tuyres, by changing the quantity of blast supplied perunit of time, if required, with a simultaneous charge of the pressure ofthe blast. Then, by an increased supply of blast with a maintenance ofthe usual quantities of coke, an heightening of said layer or zone canbe obtained with the stated action upon an increase of the carboncontent of the smelting finally produced.

Thorough experiments have unobjectionally proved the effectiveapplicability of the new rules upon which the improved method is based.The details of the latter depend, of course, upon the dimensions and theconstruction ofthe cupola furnace used and can be easily determined foreach individual case by a series of'trials.

What I claim, is: v

1. The method of operating a cupola furnace in the production of castiron which consists in introducing into the furnace chamber a charge ofiron and coke, at least 50% of the iron so introduced being in the formof steel or wrought iron of low carbon.

content and the coke comprising not more than about 13% of the totalchar e, submitting the charge, after ignition of t e coke, to theactionof an air blast under water gauge pressure 'ofbetween 400 and 800mm. to effect smelting of the metallic charge, whereby amolten metal ofrelatively low carbon content but extremely high temperature isproduced, and thereafter passing this supercrease the carbon contentthereof.

2. The method set forth in claim 1 which includes the step of regulatingthedegree of carbonization below the tu res by va the height of thetuyres a ove the ttom.`

In testimony' whereof I have hereunto set my hand: v

KARL EMMEL.

